The present invention relates to an apparatus and a method for washing both surfaces of a substrate such as a semiconductor wafer and an LCD (liquid crystal device) substrate.
In the manufacturing step of a semiconductor device, a photolithographic technique is employed for forming a circuit, an electrode pattern etc. on the semiconductor wafer. In the photolithographic process, the semiconductor wafer is first coated with a photoresist solution. Then, the coated resist is exposed to light, followed by being developed with a developing solution. It should be noted that, before a series of resist processing noted above, a front surface of the wafer which is to be coated with a resist solution, is washed in order to prevent defect occurrence in the circuit pattern and short-circuiting of the wiring. It is also necessary to wash a back surface of the wafer in order to prevent a focus error during the light-exposure step and particle generation.
It was customary in the past to use a scrub-washing device for washing both surfaces of a semiconductor wafer with a brush, while supplying a washing liquid to the semiconductor wafer. In general, the washing device of this type includes a front surface washing unit, a back surface washing unit, a wafer reversion unit, and a heating/cooling unit, which are arranged with the transfer path sandwiched therebetween. Furthermore, the washing device has a wafer transfer arm mechanism moving on the transfer path. When the washing device is used for washing both surfaces of the semiconductor wafer, the wafer is transferred by a transfer mechanism into each of the units by the wafer transfer arm mechanism in accordance with a predetermined recipe, thereby applying a series of washing treatments to the wafer.
In the substrate washing treatment of this type, it takes long time to wash a substrate since both surfaces are washed separately. It follows that users desire to improve a throughput for the washing process.
In the conventionally-used process, a front surface of a wafer is first washed, heated, and cooled. The wafer is then reversed to wash the back surface thereof. The resultant wafer is reversed again and subjected to heating and cooling steps. Thus, the wafer is washed in the fixed manner mentioned above without flexibility. In these circumstances, users requires to wash a substrate in a more flexible manner. However, it is insufficient for the conventional both-surface washing apparatus to satisfy the aforementioned requirements.